Revert "net: add exit_batch_rtnl() method"

This reverts commit 21313155 which is
commit fd4f101edbd9f99567ab2adb1f2169579ede7c13 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I164d68cc594a2e25999bdf1c1346b3792766a9c0
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>